<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>01_JS的三种引入方式</title>
<!-- 引入外部JS文件 -->
  <script src="01.js">
    console.log('我是外部JS文件！我没被执行')
  </script>
</head>
<body>
  <button onclick="alert('请先登录！')">点击登录</button>
  <button onclick="console.log('点我干嘛')">点我</button>
  <h1 id="aaa">我是一级标题</h1>
  <script>
    console.log('我是内部JS,我被执行了！');
    console.log(aaa)
  </script>
</body>
</html>
